KEY TO PLATE III 



Oysters from 1 to 60 mm. i._V, to 2f inches) in length, n; 

 size, in the same position throughout, from the right side. 



First line from left to right: 1, 1-5. 2, 2-5, 3, 3-5, 4, 4-5, 5 mm. 

 Second line: 6, 7, 8, 9, 10, 11, 12 mm. 

 Third line: 14, 16, IS, 20, 22 mm. 

 Fourth line: 25, 30, 35, 40 mm. 

 Fifth line: 50, 60 mm. 



(Drawn by Mr. F. W. Parker, of Halifax, N.S., medical student at 

 McGill University, from specimens of the author's selection and under his 

 directions). 



